The total synthesis of the pentacyclic camptothecin analogues 3 and 4 in 11 steps from p- tolualdehyde is described. The overall shape of compound 3 is the same as that of potent, naturally occurring camptothecin (la). Despite the near spatial identity of 3 and lb (racemic,(BORS)-camptothecin) from a three-dimensional standpoint, the 9KB and 9PS cytotoxicity assays indicate at least a 40-60-fold decrease in activity of 3 compared to that ...
